Transport of proteins and sulfated mucopolysaccharides in the goldfish visual system

Abstract

SUMMARY "-Proline, "H-asparagine and Na2W04 have been found to be highly specific markers for axonal transport in the goldfish visual system. The amino acids label both rapidly and slowly transported proteins while the 35S is recovered mainly with the rapidly transported materials, including protein-bound mucopolysaccharides. These precursors have been used t o study the rate of transport, the subcellular distribution and the rate of turnover of transported proteins in the nerve terminals.

The Polypeptide Composition of Intra-axonally Transported Proteins: Evidence for Four Transport Velocities

“…The phenomenon of intra-axonal transport of protein is generally considered to include a "slow" component (transported at a rate on the order of 1-5 mm/day) and a "fast" component (transported at a rate on the order of hundreds of millimeters per day) (1-3). Proteins transported "rapidly" differ from those transported "slowly" with regard to their subcellular distribution (4)(5)(6), their oligosaccharide content (4,(7)(8)(9), and their electrophoretic mobility (9)(10)(11)(12). Thus, the "rapid" and "slow" components of intra-axonal transport are defined not only by their velocity of transport, but also by their composition.…”

Axonal transport of proteoglycans to the goldfish optic tectum

“…Our previous studies on pronase digests of transported molecules have shown that both chondroitin sulfate (4 or 6) and heparan sulfate undergo axonal transport in the goldfish optic nerve (16,17) and the garfish olfactory nerve (18,19). Axonal transport of the same two glycosaminoglycans has been reported in a similar study on the rat optic nerve (20).…”

Axoplasmic transport of a brain-specific soluble protein☆

“…Although the percent of total soluble counts in the 14-3-2 protein is about the same (Table I) for right and left (control) optic lobes, the radioactive 14-3-2 protein found in the optic lobe contralateral to the injected eye must represent axonal transport and not local synthesis since labeled amino acids per se are not transported along the axon [9,31,39]. Thus, it is evident from the data presented in Table I that the 14-3-2 is indeed transported from its site of synthesis in the retinal ganglion cells to the contralateral (right) lobe, but at a slow rate.…”

“…24 chicks were each injected intraocularly with 10 µl (0.33 mCi) of an aqueous solution of [ 3 H] proline ( 40 Ci/mmol) obtained from New England Nuclear Corp. (Boston, Mass.). Tritiated proline was used as a precursor since it has been found to produce more efficient labeling of the transported protein in both the goldfish and the chick optic systems [ 31,32), with relatively little incorporation into the brain as a whole. Furthermore, the 14-3-2 protein contains 17 residues of proline [ 33] so that reasonable amounts of isotope incorporation into newly synthesized 14-3-2 protein would be expected.…”

“…One-half of the chicks were sacrificed at 6 h and the balance at 6 days after isotope administra-tion. The time periods of 6 h and 6 days were chosen to differentiate between rapid and slow axoplasmic flow [31,34]. After decapitation, the optic lobes from each chick were dissected out on ice and the injected eye was removed.…”